(1) Field of the Invention
The present invention relates to a water filter having a filter head and an interchangeable filter cartridge with an untreated-water distribution element which is located on the filter cartridge as well as a filter head and an interchangeable filter cartridge with a blending device and an adjusting device for adjusting a partial-flow ratio between at least two flow paths in which at least one flow path is a filter section.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In order to set a predetermined water quality for the particular use, softening/decarbonizing/demineralizing systems based on interchangeable filter candles contain a blending device for coordinated mixing of water treated via the filter section with water which has not been filtered or has been conducted over a different water treatment medium.
These systems are used in the treatment of drinking water in private households and in the catering trade as a central or decentral installation for the supply of extraction points and especially for the supply of modern kitchen appliances, for example coffee machines, taps and ice-makers (for example in modern refrigerators), and furthermore in the commercial sector for the supply of drinks vending machines for the preparation of cold and hot drinks, of dishwashers and steam cookers for the purpose of optimizing the taste of the drinks and meals prepared or produced therewith, and in order to protect the machines from technical problems caused by water.
According to the prior art, there are simple solutions for this with fixed holes in the cartridge head. In these solutions, the blending water remains unfiltered and adaptation of the filter cartridge to specific requirements is not possible.
A further known embodiment option is the integration of an adjustable blending device in the head. Although the blending can be adapted individually here, the blending water cannot be filtered—for example over activated carbon, since it is guided past the filter cartridge.
Constructions with a blending device in the filter head are also already in existence, said constructions providing separate guidance of the main water flow and blending water flow to the filter cartridge, with the blending water additionally being guided via other treatment media in the cartridge. A disadvantage of this construction is the considerable complexity in the filter head because of the blending valve and the separation of three volumetric flows: a) for the treatment section, b) for the blending water section, and c) for the return of the entire filtrate. These concepts are described, for example, in DE 199 58 648 A1 and WO2004/007374 A1.
A further option is to integrate the blending valve in the cartridge. In this connection, constructions are known which permit filtration of the blending water and those which do not permit filtration of the blending water. A concept without filtration of the blending water is described, for example, in U.S. Pat. No. 6,923,910 B2. In these embodiments, the head constructions are simple, since they do not contain a blending valve and only two volumetric flows have to be guided.
Furthermore, constructions are also known which permit adjustment of the quantity of blending water in the filter cartridge. A disadvantage of the blending system which is integrated in the cartridge is the necessity, upon each change of cartridge, of having to reset the blend ratio at the filter cartridge in order to adapt the water quality again to the application. Upon a change of cartridge, errors are frequently made when adjusting the blending quantity, or the adjustment is even completely forgotten, thus giving rise to undesirable effects, such as furring up of the machines and quality problems with the prepared foodstuffs.